In general, Information Handling Systems (IHS) include a processing device, a memory device for storing computer code that, when executed by the processor, causes the IHS to perform various operations on data and a data storage device for storing the data. Components of the IHS are generally connected by data links, such as data buses or other data connections. Often, the data links include one or more pairs of conductors, which are typically configured to operate in a differential mode. One form of a data link is a High Speed Serial (HSS) link.
As demand for memory, fabric, and IO Bandwidth in an IHS increases, the number of data links in an IHS increases. For example, a typical 2014 IHS platform may have 40 pairs of QPI (Intel Corporation QuickPath Interconnect®) fabric, 80 pairs of Peripheral Component Interface Express (PCIe) gen3, and 24 or more Serial Attached SCSI (SAS) pairs. Looking forward to 2016-2018, the types, number and speed of the pairs will increase dramatically. At higher and higher frequencies, due to transmission medium losses, the power required to drive and receive the differential signals across cost-effective PCBs and cables goes up exponentially.
Transmitter (Tx) and Receiver (Rx) equalization is commonly used to ensure that high speed Serializer/Deserializer (SerDes) interfaces work error free, or at acceptably low Bit Error Rates (BER), depending on the link requirements. Receiver equalization coefficients, such as Decision Feedback Equalization (DFE), Variable Gain Amplifier (VGA) and Analog Equalization (AEQ) are effective techniques for enhancing performance. However, using these advance techniques, the transmission power of Input/Output (I/O) devices can dominate the logic/core power consumption in many devices such as PCIe or SAS switches and other I/O controllers. I/O power may be up to 70% of total chip power consumption.
High speed SerDes or Serial links have historically been differential in nature due to the advantages of differential signaling. These advantages include noise immunity, low voltage swing and provide continuous current return path. But, differential signaling also consumes twice the power and nearly twice the channel routing real estate.